Fast particle acceleration in 3D hybrid simulations of quasi-perpendicular shocks

TL;DR

This study uses 3D hybrid simulations to demonstrate that protons can spontaneously develop non-thermal tails at quasi-perpendicular shocks, revealing new insights into particle acceleration mechanisms relevant to cosmic ray origins.

Contribution

First self-consistent 3D hybrid simulations showing spontaneous non-thermal tail formation at quasi-perpendicular shocks, advancing understanding of particle acceleration processes.

Findings

Protons develop non-thermal tails spontaneously in 3D simulations.

Particles are rapidly accelerated via shock drift acceleration.

Maximum energy is limited by upstream escape.

Abstract

Understanding the conditions conducive to particle acceleration at collisionless, non-relativistic shocks is important for the origin of cosmic rays. We use hybrid (kinetic ions -- fluid electrons) kinetic simulations to investigate particle acceleration and magnetic field amplification at non-relativistic, weakly magnetized, quasi-perpendicular shocks. So far, no self-consistent kinetic simulation has reported non-thermal tails at quasi-perpendicular shocks. Unlike 2D simulations, 3D runs show that protons develop a non-thermal tail spontaneously (i.e., from the thermal bath and without pre-existing magnetic turbulence). They are rapidly accelerated via shock drift acceleration up to a maximum energy determined by their escape upstream. We discuss the implications of our results for the phenomenology of heliospheric shocks, supernova remnants and radio supernovae.